This invention pertains to an operator for a casement-type window which causes the window sash to move between open and closed positions and wherein the operator has torque performance advantages in opening and closing of the window as well as better action in holding of the window in a fixed, partially open position.
Operators for casement-type windows are known in the art wherein linkage connected between the window frame and the window sash move the window sash between open and closed positions by a combined pivoting and linear movement. In opening movement of the window sash, one edge thereof is caused to move outwardly from the window frame, while the other edge of the window, which is suitable supported by slider structure at the top and bottom thereof, is caused to move linearly in a path parallel to the window sill and, at the same time, pivoting is permitted. Typically, the prior art operators have had linkage structure which is incapable of exerting substantial force during final closing movement of the window sash or upon initial opening thereof. In order to overcome these deficiencies, there is an operator, as shown in Evers U.S. Pat. No. 3,438,151 which has added structure to assist in final closing of the window and also to assist in initial opening thereof. The assist structure shown in the Evers patent is only effective during a very limited range of movement of the window sash toward and away from the final closed position.
A relatively complex structure of an operator for a casement-type window is shown in Hagstrom U.S. Pat. No. 2,366,613 wherein threaded members transport structure which supports the window sash and a separate member operable by the transport structure provides torque assistance in opening and closing of the window. The Hagstrom structure is complex and bulky and does not disclose a practical solution to a low-cost operator for a casement-type window.